Soil water repellency development in amended sand rootzones

Particulate organic matter (OM) and surface area–limited sands are associated with soil water repellency (SWR) in turfgrass systems. The increasing ubiquity of amended sand rootzones warrants investigation of factors contributing to SWR. Our objective was to identify how amendment type and/or inclusion rate affect rootzone SWR over a range of irrigation regimes. A U.S. Golf Association–specified sand was amended with dried turfgrass roots and either sphagnum peat moss (SPM), reed sedge peat (RSP), biosolid compost (BSC), or calcined clay (CC) at 0, 0.1, or 0.2 m3 m–3. Mixes were saturated, gravitationally drained, incubated under isothermal ventilation having mean vapor pressures of 1.78, 2.19, or 2.45 kPa, and reirrigated when matric tension exceeded 300 kPa. After 138 d, rootzone subsamples were eluted of particulate OM before measuring mineral-adsorbed hydrocarbon content (MAHC) by infrared spectroscopy. The repellency index was used to quantify SWR of intact (Rintact) and eluted (Reluted) samples. Amendment rate (0.2 > 0.1 > 0 m3 m–3) and type (BSC > RSP = SPM > CC) significantly affected Rintact. Only CC-amended rootzones were more wettable than the control. Severely elevated Reluted and MAHC were observed in all sands amended by BSC. Inclusion of SPM or RSP at 0.1 m3 m–3 resulted in Reluted and MAHC values statistically equivalent to the control rootzone. At 0.2 m3 m–3 inclusion, all organic amendments significantly increased Reluted and MAHC relative to the control (BSC > RSP = SPM).

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